This invention relates to auxiliary power steering systems of the dual power type wherein two separate servomotors respectively supplied with pressurized fluid from separate pumps through separate control circuits jointly perform the vehicle steering operation in response to rotation of a common steering spindle associated with one steering gear assembly through which the supply and exhaust of fluid to both servomotors is controlled.
The foregoing type of auxiliary power steering system is generally well known, as disclosed for example in U.S. Pat. No. 3,822,759. In this type of auxiliary power steering system, two mutually separated hydraulic steering circuits are controlled by means of a common steering spindle. One steering control circuit is associated with a steering gear assembly within which one of the servomotors is located drivingly connected through gear and steering linkages to the dirigible wheels of the vehicle. The other steering circuit is associated with a second control valve coaxial with the first control valve for operation of the second servomotor with which gearing and steering linkages are also associated for joint powered steering of the vehicle. Separate servo pumps and reservoirs are assigned to the two steering control circuits.
It is therefore an important object of the present invention to provide an auxiliary power steering system of the foregoing type that may be manufactured in an economic fashion for use in a dual power system and with little change for use in a single circuit power steering system. A further object is to provide an auxiliary power steering system that is compact in both its axial and radial extent.